Dick Allen quoted thusly:

> R.E. Snodgrass writes this: "It is particularly difficult to understand how
> colors are distinguished, since there is no known mechanism in the insect
> corresponding to the rods and cones of a vertebrate eye."

This is apparently an older publication.  There are multiple references citing
the exact nature of bee vision, and listing the exact types of sensors that
bees have.

Do a web search on "ommatidia" and "bee", and read all about them.

        jim